Known catalyst substrate articles for engine aftertreatment systems include a catalyst substrate material wrapped in a ceramic fiber mat, which is then encased in a metal shell or skin. The catalyst substrate material may be a ceramic material, such as cordierite or silicon carbide. Catalyst components are known to suffer damage from thermal stresses, for example from temperature expansion differences between the substrate material and the housing material. The use of a ceramic fiber mat allows for expansion of the substrate within the housing, but introduces significant cost, manufacturing complexity, and provides for wasted space in the catalyst housing that cannot participate in active treatment of gases within the housing. Therefore, further technological developments are desirable in this area.